Figure 4: Low-end linear curves of colorimetric and luminescent ELISA at concentrations ranging from 0.034 to 2.743 ng/ml. The mean signal value ± standard deviation from triplicate wells was plotted against standard concentration by a linear fit method. Larger variations are observed in colorimetric method at this concentration range. The standard curve is also less linear than luminescent ELISA (R2=0.961 vs. 0.992).